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I'm just starting in on the New York Inventory shelves at CenterStaging's Burbank, CA facility, and pulled down a Fender Twin Reverb, it having a RED gaffers tape note on the top, stating suspect Foot Pedal Jack, and the Reverb thought to be intermittent. I moved it to my check-out bench, back side facing me. Removed the upper rear panel to get access to the tubes and jacks. No Foot Pedal in the cabinet, so I went back to the shelves, felt in the cavity of a couple other Twins, and came back with one, it's cord wrapped up tight, for endless curly-cues.
While the amp was now plugged in and warming up, I took the pedal to my test bench, grabbed my tiny machinist vise, set it to grip the plug firmly so I could unscrew the binder-head screws and have a look at the plug wiring. AS I wasn't surprised to find, the exposed lead lengths of the inner insulated wires were shorting to each other and the shell, so I had to cut off the end and re-terminate the plug properly. I've never been a big fan of Fender's choice in this 3-core shielded wire plus unshielded wire side-by-side in that stiff vinyl jacket. It took two attempts at creasing the jacket with my X-Acto knife to separate and remove it without loosing shield strands. Then, unsoldered the left-over cable end from the terminals, and desoldered the ring lug and tip in prep for the newly prepared ends.
Stripping those two white insulated wires is a task I turn to my Erem 504 End-strippers, as they can get in from the end of the wires without being obstructed by the shortness of the other wires. Got the plug re-wired, then milked the jacket to get all of the jacket to lay under the 'fingers' of the top/bottom cable grip of that flat plug, and tightened it back up. I then uncoiled and milked the cable a bunch to try and get the memory of the tight coiling to straighten out.
Took the pedal over to the amp, it now more than warmed up. I didn't plug anything in yet. Turned both channel's volume controls CCW, and switched out of S/B. Noisy. Turned the Reverb level CCW, set the tone controls half-way. Still noisy. Turned up Normal Ch, not adding to the noise. Turned up Vibrato Ch, and it got worse, so, switched back to S/B, and removed the tube shields for V2, V4 and V5. I swapped V2 (Vibrato preamp tube) with V4 (Reverb Return and Mixer tube). No difference, so returned them as they were, then swapped V2 with V5 (Vibrato tube). Switched out of S/B, and now, the amp sounds quiet. I've never found problems with moving a noisy tube over to the Vibrato ch, if it's not outrageously bad.....though sometimes that Vibrato tube is just as bad as the noisy tube, so never know. Worked this time.
Now, checked residual noise, turning up the Normal Ch Volume to give a listen. Racked the tone controls back and forth, Bright switch on/off. Nominally quiet. Turned it down CCW, and did the same with the Vibrato Ch. Reverb was CCW. All was nominally quiet. Turned up the Reverb, and did hear the traditional added noise from the reverb tank, tapped on the tank to hear it respond to the touch. Turned the Reverb back CCW, turned the volume CCW.
Then, I plugged in the freshly terminated Foot Pedal plug. I got a loud pop. Turned the Vibrato Ch up, Reverb up, and verified I could turn the Reverb on and off. Did the same turning the Vibrato on and off, checking the Vibrato speed and intensity with just the residual channel noise. All ok. Switched the Vibrato off again. Turned the volume CCW. Then, unplugged the pedal plug. Loud Pop. I fetched my TRS shorting plug that I use when there's no pedal handy. No noise inserting or removing it.
Why is this pedal causing the amp to pop when I plug it in, amp NOT in Standby. Ah....could it be the Tip of the TRS plug on the pedal is not switched on (shorting the tip to ground)? I pushed the Vibrato button, and plugged that pedal back in. Now, NO LOUD POP. Figures. Get far enough away from remembering these little tidbits of knowledge, and forget what causes problems. That explained the note on the cabinet suggesting the Footpedal jack on the rear panel was bad. My TRS shorting plug for turning on Reverb and Vibrato shorts Tip and Ring to the Shell.
While the amp was now plugged in and warming up, I took the pedal to my test bench, grabbed my tiny machinist vise, set it to grip the plug firmly so I could unscrew the binder-head screws and have a look at the plug wiring. AS I wasn't surprised to find, the exposed lead lengths of the inner insulated wires were shorting to each other and the shell, so I had to cut off the end and re-terminate the plug properly. I've never been a big fan of Fender's choice in this 3-core shielded wire plus unshielded wire side-by-side in that stiff vinyl jacket. It took two attempts at creasing the jacket with my X-Acto knife to separate and remove it without loosing shield strands. Then, unsoldered the left-over cable end from the terminals, and desoldered the ring lug and tip in prep for the newly prepared ends.
Stripping those two white insulated wires is a task I turn to my Erem 504 End-strippers, as they can get in from the end of the wires without being obstructed by the shortness of the other wires. Got the plug re-wired, then milked the jacket to get all of the jacket to lay under the 'fingers' of the top/bottom cable grip of that flat plug, and tightened it back up. I then uncoiled and milked the cable a bunch to try and get the memory of the tight coiling to straighten out.
Took the pedal over to the amp, it now more than warmed up. I didn't plug anything in yet. Turned both channel's volume controls CCW, and switched out of S/B. Noisy. Turned the Reverb level CCW, set the tone controls half-way. Still noisy. Turned up Normal Ch, not adding to the noise. Turned up Vibrato Ch, and it got worse, so, switched back to S/B, and removed the tube shields for V2, V4 and V5. I swapped V2 (Vibrato preamp tube) with V4 (Reverb Return and Mixer tube). No difference, so returned them as they were, then swapped V2 with V5 (Vibrato tube). Switched out of S/B, and now, the amp sounds quiet. I've never found problems with moving a noisy tube over to the Vibrato ch, if it's not outrageously bad.....though sometimes that Vibrato tube is just as bad as the noisy tube, so never know. Worked this time.
Now, checked residual noise, turning up the Normal Ch Volume to give a listen. Racked the tone controls back and forth, Bright switch on/off. Nominally quiet. Turned it down CCW, and did the same with the Vibrato Ch. Reverb was CCW. All was nominally quiet. Turned up the Reverb, and did hear the traditional added noise from the reverb tank, tapped on the tank to hear it respond to the touch. Turned the Reverb back CCW, turned the volume CCW.
Then, I plugged in the freshly terminated Foot Pedal plug. I got a loud pop. Turned the Vibrato Ch up, Reverb up, and verified I could turn the Reverb on and off. Did the same turning the Vibrato on and off, checking the Vibrato speed and intensity with just the residual channel noise. All ok. Switched the Vibrato off again. Turned the volume CCW. Then, unplugged the pedal plug. Loud Pop. I fetched my TRS shorting plug that I use when there's no pedal handy. No noise inserting or removing it.
Why is this pedal causing the amp to pop when I plug it in, amp NOT in Standby. Ah....could it be the Tip of the TRS plug on the pedal is not switched on (shorting the tip to ground)? I pushed the Vibrato button, and plugged that pedal back in. Now, NO LOUD POP. Figures. Get far enough away from remembering these little tidbits of knowledge, and forget what causes problems. That explained the note on the cabinet suggesting the Footpedal jack on the rear panel was bad. My TRS shorting plug for turning on Reverb and Vibrato shorts Tip and Ring to the Shell.